Playstation 4 Audio DSP Based On AMD’s PC TrueAudio Technology

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The Playstation 4’s audio chip has remained somewhat of a mystery until recently, when during AMD APU2013 conference AMD revealed the PS4’s audio chip is based on their TrueAudio API and chip technology technology. Let’s explore exactly what AMD’s true audio technology is, and how it will benefit not only the PS4 but possibly PC Gaming too.

AMD have been very much in the thick of things recently, not only have started pushing their Mantle API, but also reintroducing the concept of hardware accelerated audio processing – which they have dubbed TrueAudio. Traditionally, audio processing is done on the CPU but isn’t an ideal situation, as it can be extremely costly on CPU resources, especially when you’re dealing with surround sound positional audio. For example, on the Microsoft’s Xbox 360 several developers have commented that processing audio used up between one to two hard threads of the X360. When you factor into that there’s only 6 threads total available for the Xbox 360, and you can see how it becomes costly very quickly. To understand the PS4’s audio DSP chip, it’s important that we have a solid understanding of its purpose in the PC space and thus how it will not only benefit the PS4, but also how AMD will plan to leverage it to gain traction in the PC market.

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The TrueAudio DSP has been integrated into the recent AMD Radeon R9 and R7 graphics cards (for example the Radeon R9 290x) and this very chip has served as the basis of the Playstation 4’s audio processor. Back in the late 90’s and early 2000’s there was a lot of movement in the sound card industry – running alongside the GPU race. However, for various reasons the advancements in sound began to slow down. One of the major reasons behind this was actually Microsoft’s Windows Vista. It moved most of the audio stack to software (wiki link). This was a significant shift from previously, as they had been mostly handled through the sound cards drivers. This meant that a lot of the processing could be shifted on the sound card. In short, when 3d sound was needed to be processed the sound card was told what to do and it pretty much went ahead and did its thing. Vista simplified this, and also many motherboards were fitted with a Realtek AC97 audio compatible sound system and therefore, much of the progress was lost.

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Benefits to real time Audio processing for PC and PS4

Yeah, but 3d sound is still alive and well, I hear you cry. This is true, the games engine is left to do the processing – by shifting that work on to the CPU itself. There’s a set amount of CPU utilization that audio is able to be given, and this goes doubly for consoles. While PC gamers can technically just throw in a faster CPU if need be, the PS4 can’t do this. Despite the fact its CPU is highly multi threaded (using the AMD Jaguar SoC), there’s still finite resources to go around.

From the perspective of Sony’s Playstation 4, the inclusion of a TrueAudio chip isn’t exactly a large shock for a few reasons. Firstly, the PS4’s GPU is already very similar to the AMD Volcanic Islands (which power the R9 290X) in terms of the way it handles Compute for example. Additionally, the space taken up ‘on-die’ is pretty small. It’s a smart use of space for the performance benefit of off-loading work from the CPU.

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As of the time I’m writing this (mid november 2013) AMD haven’t released their TrueAudio API for the PC. But due to the PS4’s use of the technology it’ll likely help ‘smooth over’ one of the biggest hurdles – developers actually using it for the PC. Pretty much, just like their Mantle API it doesn’t just work, developers need to code for it specifically. If there’s already a decent portion of the work that’s already done due to the TrueAudio DSP being pretty much implemented in the PS4, then it’ll be much more likely developers will go ahead and program for it.

To be clear, the Audio DSP from AMD’s TrueAudio and the Playstation 4 aren’t anything new or shiny. Remember earlier how we’d discussed that there’d been a significant movement in the audio industry from the late 90’s to the 2000’s? Well, during that time companies like Creative Labs were pushing out super powerful audio DSP’s. It’s just that they’ve not really been popular – or taken seriously, since that point.

While basic audio calculations aren’t too expensive to run (in other words, eat up much CPU time), and this includes basic 3d effects which are precomputed, real-time effects are very costly. For example, multiple real time reverb on a pair of 7.1 speakers will leave your CPU struggling like a snail trying to climb Mount Everest. Thing is, they are the cooler sound effects and one could argue that they are needed to help bring a realistic atmosphere into gaming. Lets face facts, we gamers expect a shot to sound awesome if we’re in an underground bunker. Or the sound of a monster through trees to sound properly distorted and so on.

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Implementing TrueAudio technology with games

AMD have already started approaching games developers in the PC space, and of course this is only going to be encouraged by developers who will be producing PC and PS4 versions of titles. Similarly, there will be a series of plugins for the PC which will act as middleware (wiki link) to help facilitate the uptake of TrueAudio for the PC.  Because the AudioDSP isn’t a traditional sound card it means that the processed audio can be used no matter how the sound has been processed. Be it from HDMI to a TV, a USB pair of headphones, or even a 7.1 pair of speakers. But what it will mean for the PC is that developers will need to support it – for example, release a patch.

For Sony’s Playstation 4, this is all very good news indeed. Consoles have always heavily relied on their powerful dedicated processors (for Graphics) for example to help push games. Microsoft’s Xbox One also has a custom built audio processor – but that’s being used for many things, including kinect. For AMD’s Radeon graphic card they’re using the Tensillica audio DSP – which is a somewhat off the shelf component. It’s somewhat of a mixture of a fixed function and a fully programmable processor. This means that power costs along with the size of the thing are minimal and yet is pretty damn flexible. From what we understand much of the hardware is being programmable in versions of the C language.  We don’t have huge amounts of info on their inner workings yet, we can possibly guess some type of VLIW (Very Long Instruction Word – wiki link) design.

On the Radeon cards each DSP will come equipped with 32KB of Instruction and Data Cache, lovingly paired with 8KB of scratch RAM. There’s also 384KB of shared cache that’s available for all of the Audio DSP’s. On the AMD Radeon GPU’s it can also access up to 64MB of VRAM (Video RAM). Likely there’ll be either 4 or 8 audio DSP’s on the board. Interestingly enough, the low end Radeon cards have exactly the same performance from the audio DSP as the higher end cards.  For the Playstation 4 system, less is known but we can bet that it’ll be similar enough to where we’re able to draw a comparison. Otherwise, if there wasn’t at least some level of parity developers and AMD wouldn’t be able to start pushing the technology.

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The technology itself has been proven and the immediate uses for it are obvious to all. For the Playstation 4 it’ll be a fantastic addition to Sony’s machine from their perspective. It’ll reduce the load on the CPU, be fairly easy for games developers to utilize and was cheap enough to not drive the costs up sky high. For the PC gamer, it’s still unknown if the technology will be adopted for PC games developers. It’s likely that at least some will try it out, there are murmurings that Edios for instance wish to give it a test drive. The problem is that they could be effectively developing for only 50 percent (or less) of their customers – in other words, those with an AMD card. However, audio technology is surely lacking behind the march of RAM, CPU’s and certainly graphics cards.

Realistic positional audio is vital, and just think of how many sound effects are going off the next time you’re firing up a game of Battlefield 4. Or perhaps you’re playing Batman Arkam Origin’s and trying to get a clue of where the evil henchmen are. Let’s hope either TrueAudio or an alternative takes off, shal we?

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